Buggy code:
public void setOld ( boolean b ) { } public void setClasspath ( Path src ) { } public Path createClasspath ( ) { } public void setClasspathRef ( Reference r ) { } public void setBootclasspath ( Path src ) { } public Path createBootclasspath ( ) { } public void setBootClasspathRef ( Reference r ) { } public void setExtdirs ( String src ) { } public void setVerbose ( boolean b ) { } public void setLocale ( String src ) { } public void setEncoding ( String enc ) { } public void setVersion ( boolean src ) { } public void setUse ( boolean b ) { } public void setAuthor ( boolean src ) { } public void setSplitindex ( boolean b ) { } public void setWindowtitle ( String src ) { } public void setDoctitle ( String src ) { } public void setHeader ( String src ) { } public void setFooter ( String src ) { } public void setBottom ( String src ) { } public void setLinkoffline ( String src ) { } public void setGroup ( String src ) { } public void setLink ( String src ) { } public void setNodeprecated ( boolean b ) { } public void setNodeprecatedlist ( boolean b ) { } public void setNotree ( boolean b ) { } public void setNoindex ( boolean b ) { } public void setNohelp ( boolean b ) { } public void setNonavbar ( boolean b ) { } public void setSerialwarn ( boolean b ) { } public void setStylesheetfile ( File f ) { } public void setHelpfile ( File f ) { } public void setDocencoding ( String enc ) { } public void setPackageList ( String src ) { } public Javadoc . LinkArgument createLink ( ) { } public class LinkArgument { private String href ; private boolean offline = false ; private String packagelistLoc ; public LinkArgument ( ) { } public void setHref ( String hr ) { } public String getHref ( ) { } public void setPackagelistLoc ( String src ) { } public String getPackagelistLoc ( ) { } public void setOffline ( boolean offline ) { } public boolean isLinkOffline ( ) { } } public Javadoc . GroupArgument createGroup ( ) { } public class GroupArgument { private String title ; private String packages ; public GroupArgument ( ) { } public void setTitle ( String src ) { } public String getTitle ( ) { } public void setPackages ( String src ) { } public String getPackages ( ) { } } public void setCharset ( String src ) { } public void setFailonerror ( boolean b ) { } public void execute ( ) throws BuildException { if ( "javadoc2" . equals ( taskType ) ) { log ( "!!<seq2seq4repair_space>javadoc2<seq2seq4repair_space>is<seq2seq4repair_space>deprecated.<seq2seq4repair_space>Use<seq2seq4repair_space>javadoc<seq2seq4repair_space>instead.<seq2seq4repair_space>!!" ) ; } if ( ( sourcePath ) == null ) { String msg = "sourcePath<seq2seq4repair_space>attribute<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>set!" ; throw new BuildException ( msg ) ; } log ( "Generating<seq2seq4repair_space>Javadoc" , MSG_INFO ) ; Commandline toExecute = ( ( Commandline ) ( cmd . clone ( ) ) ) ; toExecute . setExecutable ( "javadoc" ) ; if ( ( classpath ) == null ) classpath = Path . systemClasspath ; else <START_BUG> classpath = classpath . concatSystemClasspath ( ) ; <END_BUG> if ( ! ( Javadoc . javadoc1 ) ) { toExecute . createArgument ( ) . setValue ( "-classpath" ) ; toExecute . createArgument ( ) . setPath ( classpath ) ; toExecute . createArgument ( ) . setValue ( "-sourcepath" ) ; toExecute . createArgument ( ) . setPath ( sourcePath ) ; } else { toExecute . createArgument ( ) . setValue ( "-classpath" ) ; toExecute . createArgument ( ) . setValue ( ( ( ( sourcePath . toString ( ) ) + ( System . getProperty ( "path.separator" ) ) ) + ( classpath . toString ( ) ) ) ) ; } if ( ( version ) && ( ( doclet ) == null ) ) toExecute . createArgument ( ) . setValue ( "-version" ) ; if ( ( author ) && ( ( doclet ) == null ) ) toExecute . createArgument ( ) . setValue ( "-author" ) ; if ( ( Javadoc . javadoc1 ) || ( ( doclet ) == null ) ) { if ( ( destDir ) == null ) { String msg = "destDir<seq2seq4repair_space>attribute<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>set!" ; throw new BuildException ( msg ) ; } } if ( ! ( Javadoc . javadoc1 ) ) { if ( ( doclet ) != null ) { if ( ( doclet . getName ( ) ) == null ) { throw new BuildException ( "The<seq2seq4repair_space>doclet<seq2seq4repair_space>name<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>specified." , location ) ; } else { toExecute . createArgument ( ) . setValue ( "-doclet" ) ; toExecute . createArgument ( ) . setValue ( doclet . getName ( ) ) ; if ( ( doclet . getPath ( ) ) != null ) { toExecute . createArgument ( ) . setValue ( "-docletpath" ) ; toExecute . createArgument ( ) . setPath ( doclet . getPath ( ) ) ; } for ( Enumeration e = doclet . getParams ( ) ; e . hasMoreElements ( ) ; ) { Javadoc . DocletParam param = ( ( Javadoc . DocletParam ) ( e . nextElement ( ) ) ) ; if ( ( param . getName ( ) ) == null ) { throw new BuildException ( "Doclet<seq2seq4repair_space>parameters<seq2seq4repair_space>must<seq2seq4repair_space>have<seq2seq4repair_space>a<seq2seq4repair_space>name" ) ; } toExecute . createArgument ( ) . setValue ( param . getName ( ) ) ; if ( ( param . getValue ( ) ) != null ) { toExecute . createArgument ( ) . setValue ( param . getValue ( ) ) ; } } } } if ( ( bootclasspath ) != null ) { toExecute . createArgument ( ) . setValue ( "-bootclasspath" ) ;

Fix:
classpath = classpath . concatSystemClasspath ( "ignore" ) ;